This invention relates generally to a telephone test instrument and more particularly, but not by way of limitation, to a telephone technician's hand-set used in testing subscriber loops of a telephone network.
A conventional telephone instrument through which telephone calls are made is referred to as a telephone subscriber set. A subscriber set at a home or business, for example, is connected to a local switching center of the telephone network through wires which extend between the location of the subscriber set and the location of the local switching center. The two wires to which the subscriber set connects are designated tip and ring lines, and the circuit defined from the local switching center to the subscriber set through the two wires is referred to as a subscriber loop.
When the subscriber who has the set reports a problem with the telephone circuit, a telephone technician can go to locations along the subscriber loop and connect a portable telephone test instrument, sometimes called a butt-set, across the two wires. Such a test instrument of the type to which we are referring has at least the capability of transmitting voice signals onto and receiving voice signals from the connected loop. typically such an instrument can selectably monitor or seize the circuit, dial into a seized circuit and conduct voice communications. Specific types of such test instruments have various other capabilities. Although such various test instruments exist, there is the need for an improved instrument having other and improved features.